Process feed gas in an LNG plant generally goes through a series of pre-treatment stages to remove acid gas, mercury and moisture and avoid freezing or corrosion problems in the cryogenic section. A generic single mixed refrigerant (SMR) liquefaction cycle may be used to cool and liquefy process feed gas such as, for example, natural gas. The process feed gas typically passes through a heat exchanger with the SMR for cooling the process feed gas that is used for producing LNG. The SMR is cooled using a primary cooling system comprising water at a temperature that is—around 25° C. The primary cooling system may include one or more heat exchangers for cooling the SMR with the cooling water before it passes through the heat exchanger with the process feed gas. The SMR liquefaction cycle may include one or more compressors for circulating the SMR through the one or more heat exchangers and a separator. The compressors are typically driven by a gas turbine engine that produces waste heat in the form of a hot combusted gas,
A generic SMR liquefaction cycle requires about 40 MW to produce 1 million tons per annum (MTPA) of LNG. If the process feed gas was cooler, then the amount of LNG produced may be increased or the same amount of LNG may be produced with less energy consumption. In addition, the cooling water used in the primary cooling system and the waste heat from the gas turbine are not recycled or used in any supplemental manner to improve the efficiency of a liquefaction cycle for producing LNG.